Drying characteristics of food materials injected with organic solvents in a fluidized bed of inert particles under reduced pressure

We tested a new fluidized-bed drying method using balls of mixed rice and soybean protein powders. The aim of the study was to determine whether the new technique increased the falling drying rate of the wet food product. The samples were injected with a small amount of ethanol, a low-boiling organic solvent, and the material was dried in a fluidized bed of inert particles under reduced pressure. The drying rate was higher for the samples injected with ethanol than for the noninjected samples. The dried ethanol-injected samples had large pores on their surfaces, while such pores were not observed for noninjected samples. We also investigated isopropanol and ethyl acetate as potential low boiling point organic solvents for sample preparation. Similar to ethanol, ethyl acetate increased the drying rate of the wet samples compared to that of their noninjected samples. In contrast, isopropanol injection had no significant effect on the drying rate.